दो या दो से अधिक पदार्थों के समांगी मिश्रण को विलयन कहते हैं। किसी निश्चित तापमान पर विलयन के उपादानों का आपेक्षिक अनुपात एक सीमा तक परिवर्तित किया जा सकता है। जब नमक को पानी में घोला जाता है तो एक समांगी मिश्रण बनता है। यह समांगी मिश्रण नमक का पानी में विलयन कहलाता है। विलेय + विलायक = विलयन

In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. If the attractive forces between the solvent and solute particles are greater than the attractive forces holding the solute particles together, the solvent particles pull the solute particles apart and surround them. These surrounded solute particles then move away from the solid solute and out into the solution. The mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation. The solution usually has the state of the solvent when the solvent is the larger fraction of the mixture, as is commonly the case. One important parameter of a solution is the concentration, which is a measure of the amount of solute in a given amount of solution or solvent. The term "aqueous solution" is used when one of the solvents is water.